Filter structure for dishwashers



Get. 13, 1970 K. RADACH 3,533,841

FILTER STRUCTURE FOR DISHWASHERS Filed Aug. 14. 196s 2 sheets-shewn 1 FIG. l

Filed Aug. 14, 1968 2 Sheets-Sheet 2 INI/[NTOR Kurt RADACH FIG. 2

FIG.3

United States Patent O im. C1. Bosh s/z; Boni 29/06 U.S. Cl. 134-111 8 Claims ABSTRACT F THE DISCLOSURE A dishwasher includes an upright housing having a predetermined inner free cross-sectional area. A supporting rack for supporting dishes to be washed is provided in the interior of the housing. Spray means are provided for directing sprays of Washing liquid against the supporting dishes. Reservoir means is located below the supporting rack so as to collect and recover at least `some of the washing liquid so that it may be recirculated for renewed spraying against .the dishes. A filter is interposed between the supporting rack and the reservoir in the path of the liquid running off from the dishes for the purpose of filtering this liquid. The filter comprises a filter element extending over substantially the entire free cross-sectional area of the housing and being folded in zig-zag shape.

BACKGROUND OF THE INVENTION The present invention relates generally to dishwashers, and more particularly to 'filters in dishwashers.

In dishwashers the dishes to be washed are usually supported in a supporting rack consisting of wire or the like and having a generally basket-shaped configuration. Various spray nozzles are provided for directing sprays of warm water against the supported dishes, both from below and usually also from the side. The various components of the dishwasher, that is the supporting rack, the sprays with the nozzles for the washing liquid, the pump, a reservoir for collecting the washing liquid running off the dishes, and a heater for heating the wash water, are arranged in an upright housing. Generally, dishwashers provide for several washing cycles includnig at least one pre-wash cycle with warm water having a temperature of conventionally approximately 60 C., and at least one subsequent wash or rinse cycle with fresh hot water which is usually supplied at a temperature of between 8O and 90 C.

Of course, dishwashers are known for private use as well as for commercial use. Particularly in dishwashers for commercial use it is customary to recover the wash Water which has been used for the pre-rinse cycle and to use it for several additional wash cycles, always with subsequent recovery. The reason for this is that particularly in commercial dishwashers the quantity of water used per load of dishes being washed is rather large, a factor which combined with the frequency with which such dishwashers are used results in an extremely large consumption of water. Of course, the more water is used the less economical will be the operation of the dishwasher, particularly in view of the fact that if fresh water is used for every cycle, the fresh water must be heated to operating temperature whereas recirculated water is either already at proper operating temperature or, if it has slightly cooled off during the previous cycle, need undergo only an elevation of its temperature amounting to a few degrees centigrade.

However, recirculation and re-use of the water poses the problem of satisfactorily removing contaminants prior to each washing cycle, that is fiuid and other particles which have adhered to the dishes and have been removed Patented Oct. 13, 1970 from the Water during the washing cycle must be filtered out before the water can be re-used. Known dishwashers employing the recirculation of wash water use a so-called filter pot which is interposed in the pump conduit of the pump which effects the circulatory movement. This device known as a filter pot contains an apertured insert which retains the solid contaminants before the water enters the pump and is recirculated by the same to the spray nozzles. However, this arrangement suffers from various disadvantages, among the most important of which is the fact that the necessarily limited size of the device require-s unavoidably a similarly limited size of the apertured retaining member. Furthermore, and based upon the first factor just mentioned, the apertured retaining member is provided With relatively large apertures to avoid frequent clogging necessitating a shut-down of the dishwasher; the use of larger apertures, however, means that the device can retain only relatively large food particles and that its primary use is in preventing the entry of bones or other hard residual items into the pump where they could do damage. Smaller particles can pass unhindered through hte apertured retaining member with the result that the water being recirculated becomes thickly contaminated relatively quickly, thus limiting severely the number of times the water can be recirculated.

Of course, this is not satisfactory because the cleaning efficiency of the dishwasher depends upon the cleanliness of the water to a very significant extent. Attempts to retain some of the smaller particles which pass through the apertured retaining member by using spray nozzles with a rather small-dirnensioned outlet have not been able to overcome this problem. The significant quantities of small food particles able to pass through the apertured retaining member Very quickly clog spray nozzles so dimensioned. 4It has therefore been impossible to use spray nozzles having small-dimensioned outlets even if, in these known dishwashers, the water is recirculated only a few times. Spray nozzles with large-dimensioned outlets, however, eject the washing liquid at reduced speed so that the efficiency of -such dishwashers is thereby reduced even further.

It is thus a gener-al object of the present invention to overcome the aforementioned disadvantages.

A more particular object of the present invention is to provide a dishwasher having a filter means for filtering the water which is to be recirculated, which filter means is highly efiicient.

An additional object of the present invention is to provide 'such a filter means which has a very large filter surface.

A further object of the invention is to provide such a filter means which can be withdrawn, cleaned of filteredoff particles and restored into its predetermined position in the dishwasher without requiring shut-down of the dishwasher. This makes it possible to avoid shutting-down of the dishwasher, and draining of the Water therefrom, which heretofore has always been necessary in the coustructions known from the prior art. Such shut-down of the dishwasher has always been of rather extended duration because, with the Water having been drained, new water had to be brought up to the required operating temperature, which is obviously time-consuming.

SUMMARY OF THE INVENTION In pursuance of the above objects, and of others which will become apparent hereafter, one feature of my invention resides in providing, in a dishwasher, an upright housing having a predetermined inner free cross-sectional area, and support means for supporting dishes to be washed in this housing. I further provide means for directing sprays of washing liquid against the thus-supported dishes and reservoir means which is located below the support means for the purpose of recovering washing liquid which runs off from the dishes so that such liquid may be recirculated for renewed spraying against the dishes. Finally, I provide filter means which is interposed between the support means and the reservoir means in the path of liquid running off from the dishes for the purpose of filtering such liquid, and this filter means comprises a filter sheet to undulate cross-section and extending across substantially the entire inner free cross-sectional area of the housing.

The term filter sheet as herein employed is not intended to signify a substantially two-dimensional member of sheet material; rather, the filter element according to the present invention is zig-zag folded in a bellows or accordion shape as will be disclosed hereafter, but these folds are located adjacent one another so that the element itself is substantially sheet-shaped. Advantageously, the filter element is located above the upper level of water in the reservoir and it is advantageous if the filter element is supported in a suitable frame which may be withdrawn from and inserted into the housing substantially in the manner of a sliding drawer.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat schematic vertical section through a dishwasher embodying my invention;

FIG. 2 is a top-plan View of a filter element for use in the dishwasher shown in FIG. 1 and in accordance with my invention; and

FIG. 3 is a sectional side-elevation in a somewhat diagrammatic view of the embodiment shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly FIG. 1 thereof, it will be seen that the dishwasher illustrated therein has an upright housing 1. Arranged in the interior of the housing 1 is a supporting rack, basket or frame 2 onto which the dishes to be washed (not illustrated) are placed. For this purpose a door 5 is provided in the housing 1 through which the rack 2 is conventionally withdrawable at least part of the way so as to provide more ready access for the placement or removal of dishes. Upper and lower spray nozzles 3 and 4, respectively, are arranged above and below the rack 2 and spray wash water against dishes supported on the rack 2. Additionally, laterally arranged spray nozzles may be provided but are not illustrated because they are not necessary for an understanding of the invention.

Arranged below the lower spray nozzles 4 is a supporting frame 6 carrying a filter sheet element 7 which is more clearly illustrated in FIGS. 2 and 3. As shown in these figures, the filter sheet which may consist of sheet material which is apertured, of a fine-mesh wire sieve or the like, is pleated or folded in undulate form, thus providing the bellows-type or accordion type folds which are clearly visible in FIG. 3. Each of these folds comprises two mutually inclined surface portions 71 and 72, and in accordance with a currently preferred embodiment the surface portion 72 of each fold may extend almost normal to the general plane of the frame 6 whereas the surface portion 71 of each fold may rise at a much smaller angle. Between themselves, the portions 71 and 72 of each fold define a trough 73 extending in the longitudinal direction of the respective fold. The construction of my novel filter element 7 firstly provides a maximum filter surface which is much larger than if the filter element were to be planar, and again it assures that even as the filter becomes progressively clogged there will always be sufficiently free unclogged filter area not to interfere with the circulation of liquid by the pump 10 (compare FIG. l).

To facilitate removal of the filter element 7 for cleaning purposes, the housing 1 is provided with a second door identified with reference numeral 8 so that the frame 6, with the filter element 7 supported thereby, can be withdrawn through the door 8 in a manner reminiscent of the movement of a sliding drawer. The outwardly withdrawn position of the filter element 7 is identified in FIG. l in broken lines and with the reference numeral 7. In the illustrated embodiment the filter folds extend transversely of the direction of movement of the filter frame into and out of the housing 1 and the filter frame is provided with a frame-shaped insert 61 supporting the filter element 7 and provided with handles 62 and 63 so that the insert 61 and the filter element 7 can be lifted out of the frame 6.

The reservoir 9 in which the wash water is collected is provided below the filter element, advantageously in such a manner that the wash water in the reservoir 9 will always have an upper level located below the filter element 7. In other words, the wash water should advantageously not rise to the filter element 7. The pump 10 serves to circulate the water from the reservoir 9 to the spray nozzles 3 and 4 in known manner and this is not further illustrated. I have also omitted other components, such as a control device which automatically controls the operation of the various rinse and wash cycles, because all of this is conventional and well known in the art and does not constitute a part of the invention. A heater is diagrammatically illustrated and identified with reference numeral 11, serving to heat the wash and rinse water.

It will be appreciated that, after the dishes to be washed have been placed into the rack 2 and the door 5 closed, water is pressed Vby the pump 10 through the nozzles 3 and 4 to spray onto the dishes on the rack 2. This water runs off the dishes, carrying with it dislodged food particles, and passes through the filter element 7. The latter retains the food particles which initially are washed into the bottom of the respective troughs or grooves 73 so that the filter surface portions 71 and 72 of each fold remain unclogged for passage of the water and filtering thereof until such time as the entire filter becomes filled with food particles. Of course, one will not wait until this has taken place; rather, before this occurs, the filter will be withdrawn through the door 8 in the manner discussed above, and food particles retained on the filter element 7 will be removed, also in the manner outlined above. lIt is a highly advantageous concept that this cleaning of the filter element 7 can take place during a post-rinse cycle, that is at a time when the water running off the dishes will no longer be contaminated with food particles. This is possible because of the ease with which the filter may be withdrawn, cleaned of retained food particles and restored to its operative position, and this possibility in turn makes it possible to carry out the cleaning of the filter without at any time interrupting the operation of the dishwasher, it being obvious that during the post-rinse cycle or cycles, the presence of the filter element 7 is not necessary because the water contains no filterable food particles.

The present invention constitutes a highly significant advance in this field because for all practical purposes it eliminates the possibility of clogging of the dishwasher, that is of the filter as well as of the spray nozzles. The arrangement of the filter element 7 above the uppermost level of the water in the reservoir 9 makes it practically impossible for larger food particles to ever enter into the water in the reservoir 9. Thus, a dish washer constructed in accordance with my present invention may recirculate the water many more times than was heretofore possible because the small filter openings which have become possible in the filter element 7 because of the vastly increased filter surface area constantly filter the water being circulated. The use of very small filter openings, for example openings in apertured sheet metal or in mesh material, and the concomitant optimum retention of contaminating particles is made possible, on the other hand, by the fact that the filter element can be frequently cleaned of retained food particles because such cleaning can take place while the dishwasher is actually in operation and thus can be carried out frequently and without the disadvantage of having to shut down the dishwasher.

It will 4rbe understood that each of the elements described above, or two or more together, may also find a useful application in other types of consrtuctions differing from the types described above.

While the invention has been illustrated and described as embodied in a filter element for use in a dish-washer, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knoweldge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a dishwasher, in combination, an upright housing having a predetermined inner free cross-sectional area; support means for supporting dishes to be washed; means for directing sprays of washing liquid against the supported dishes; reservoir means below said support means for recovering washing liquid which runs oi from the dishes so that such liquid may be recirculated for renewed spraying against the dishes; and lter means interposed between said support means and'reservoir means in the path of liquid running off from the dishes for filtering such liquid, said ilter means comprising a filter sheet extending across substantially the entire inner free cross-sectional area of said housing and having a general plane transversely to said housing, said lter sheet comprising a plurality of elongated folds each including two mutually inclined apertured sheet portions which define with said general plane of said filter sheet respective angles one of which is substantially steeper than the other.

2. In a dishwasher as defined in claim 1, the recovered liquid forming a predetermined upper level in said reservoir, and said filter means being positioned above said upper level.

3. In a dishwasher as defined in claim 1, wherein said filter sheet has a zig-zag-shaped cross-sectional conguration.

4. In a dishwasher as defined in claim 1, wherein one of said sheet portions is wider than the other in direction normal to the elongation of the respective fold.

5. In a dishwasher as defined in claim 4, wherein the respective other sheet portions extend substantially normal to said general plane.

6. In a dishwasher as defined in claim 1, said filter means further comprising frame means holding and supporting said filter sheet.

7. In a dishwasher as defined in claim 6, said housing being provided with a door through which said frame means and said filter sheet thereon may be slidingly withdrawn in a predetermined direction to thereby make said lter sheet accessible for cleaning purposes.

8. In a dishwasher as defined in claim 1, wherein said filter sheet consists of metallic material.

References Cited UNITED STATES PATENTS 560,673 5/ 1896 Atkinson 134-111 XR 1,605,961 11/1926 Loew 134-111 1,633,396 6/1927 Clarin. 2,311,813 2/19-43 Beck et al 209-397 2,413,954 1/ 1947 Conterman 210-493 XR 2,627,863 2/ 1953 Cavicchioli 134-111 XR 2,715,405 8/1955 Frech 134-111 XR 3,070,104 12/1962 Faust et al 134-111 XR 3,159,572 12/ 1964 Ranhagen 210-493 XR FOREIGN PATENTS 1,191,335 4/1959 France. 485,368 2/ 1952 Italy.

DANIEL BLUM, Primary Examiner U.S. Cl. X.R. 210-493 

